At the present time, horizontal wells and hydraulic fracturing are the typical approaches utilized to exploit natural gas, condensate and oil from low quality shale reservoirs. Shale reservoirs include a wide range of rock types, with most being unproductive. Nevertheless, the industry has viewed these shale assets as resource plays and approached treatment under the assumption that they are homogeneous reservoirs. As such, “cookie cutter” well designs having uniform well and fracture spacing are traditionally adopted for well construction and fracture treatments.
Although efficient, there is at least one drawback to the conventional approach. In reality, the shale reservoirs are highly laminated and heterogeneous, having extreme variation in reservoir properties along the vertical direction. For example, due to variation in mechanical properties and stresses over the vertical strata, hydraulic fracture growth behavior will change significantly depending on the exact fracture initiation points and the properties around the initiation points. In some places, fracture height growth may be significant, while in other locations fracture height growth may be severely restricted. Therefore, the current approach of using the same treatment for each stage in each well can be very ineffective.
In view of the foregoing, there is a need in the art for a cost-effective wellbore optimization technique which considers the heterogeneous properties of the reservoir in determining well placement and fracture design.